Using Supercurrent Measurements to Identify True Topological Majoranas

Uppsala University physicists have used supercurrent measurements to identify ways to differentiate between true and “fake” Majorana states in one of the experimental setups used most often.

This theoretical research is a significant step toward advancing the area of topological superconductors and applications of Majorana states for developing powerful quantum computers. It is expected that new experiments that investigate this strategy will follow soon.

Majorana states occur as zero-energy states at the ends of topological superconductors (a unique kind of superconductors, materials conducting with zero resistance upon being cooled close to absolute zero temperature), where low-energy states are sturdy against defects. Majorana states exhibit peculiar properties that make them potential candidates as qubits for fault-tolerant quantum computers.

However, trivial zero-energy states that mimic Majorana states can also emerge during the experiments. The challenge faced in distinguishing between the true and the “fake” Majoranas is a problem that has hindered the experimental advancement in this field of study and has been a hurdle for experts.

In a recent study, Annica Black-Schaffer’s team has proposed a solution to this problem. The researchers simulated the whole system of one of the standard experimental setups used in developing topological superconductors as precisely as possible and acquired the main effects of all the components.

They analyzed the supercurrent (current in superconductors) between two engineered superconductors and discovered that the sign of the supercurrent reverses because of the trivial “fake” Majorana state subject to magnetic field application. By contrast, such a reversal of sign is not generated by true Majorana states.

Then, the researchers determined that supercurrents are a robust tool for unambiguously differentiating between topological Majorana states and trivial states.

This study helps and motivates experimentalists towards the proper identification of topological Majoranas by using supercurrent measurements. Our study shows that we need to carry out more exact modelling.

Jorge Cayao, Postdoctoral Researcher, Uppsala University

“It is crucial that we are certain that we have actually engineered Majorana states and not some trivial states. This study presents a way to accomplish that through supercurrent measurements,” stated Oladunjoye Awoga, PhD student at Uppsala University.